After Baron V. AUFSESS (Die Farbe der Seen. Inaug.-Diss. Muenchen 1903) the refraction of the light does not have influence on the change of the blue color water, mainly also because one can obtain green water by dissolving lime compounds/connections, yellow or brown water by solve ones of humus substances in pure water. The going by experiments of the authors, which are down partly in detail described, led however to the subsequent results: the lime compounds/connections natural water do not have inherent color and are not a cause of the much-observed green coloring in with examination appearing even clear lime water; the green, after elimination of the dyes residual coloring contained in the water is the result of the refraction of the light through invisible portion cups, which the water still includes, and whose presence can be done by an intensive light beam. The lime compounds/connections affect strongly fell in the water contained the ferric compounds/connections and with these on the humus substances, which the latter natural color water strongly change. Lime salts protect therefore the blue color water. In case of the not-blue, lime-containing, natural water an equilibrium between the cleaning effect of their lime compounds/connections results and steady influxes of the humus and ferric compounds/connections, which let disappear its brown coloring lower for itself the blue color water. The blue, more or less greenish color of the purest water give information over the point, where the equilibrium between the antagonists is fixed. Purely blue water (6 m coating thickness) becomes green by dissolving lime from Icelandic double spar; when introducing CO2 a clear, somewhat less green solution of acid calcium carbonate forms; also gypsum colors such water green. During the passage of radiation of electrical light these solutions appear, particularly the CaH2(CO3)2-containing, optically clouds, it carefully to dry was evaporated, the residue contained partially organic substance, partially SiO2 or silicates (from the glass of the container), which were contained in the solution therefore in the colloidal condition. After filtering the other Ca-containing solutions by animal charcoal these showed the same blue color as pure water. When regarding by a pipe of 6 m length appears pure water with 1/1 000 000 part ferric hydroxide brown, with 1/2 000 000 green, with 1/5 000 000 unmodified blue. With humus substances the blue color is already changed by more than 1/40 000 000 part. Ferric salts color brownish; they are particularly reduced by humus substances, in the light, sometimes partially to ferrous compounds/connections, whose color is not possible, and which with the humus substances insoluble, failing compounds to be received. To a liter of clear solution with 1/3 000 000 if part colloidal Fe(OH) 3 (to dissolve of FeCl3 in H2O) is added a same volume acid calcium carbonate or CaSO4-Solution, then a flocculation, tags begins is because of the container soil a brown, ocher-colored dirt, the water is perfectly clear, appears green and leaves a residue of CaCO3 or CaSO4 without trace iron after few instants; the sediment contains 85-90% Fe(OH)3, CaCO3 or CaSO4. Also with insoluble CaCO3 begins the flocculation of the ferric compounds/connections immediately; similarly soluble salts work; with sodium chloride (sea water) a trace remains iron in solution.